Door openers of this type have long been used in door systems, in which a locked door is to be unlocked from a point remote from said door. For example, by means of an electric signal the latch in the door frame is unlocked, so that the opening of the door is made possible. On swinging up the door the unlocked latch is at least temporarily pivoted out of its locked position. For unlocking and pivoting the latch such a door opener has various mechanical and electrical components which, prior to the installation of the door opener in the door frame, are pre-assembled with the latch.
As the position of the door in its closed position is on the one hand defined by the door frame and on the other by the latch, the position of the locking surface of the latch must be accurately matched with the bearing surface of the door on the door frame. For this purpose the position of the locking surface of the latch is determined by measurement and calculation. A risk then exists that the position of the latch is not sufficiently precisely or is incorrectly determined. After fitting the door opener in the door frame the clearance of the closed door in said frame is consequently too large or too small, so that it is necessary to dismantle the door opener and carry out a readjustment. For readjustment purposes use is e.g. made of spacing plates parallel to the bearing surface and which can be inserted or removed with the latch between a locking plate and a door opener unit. If, following the installation of the door opener there is once again an incorrect positioning in the door frame, this readjustment process must be repeated until the desired clearance of the door in its closed position is adequately precisely obtained.
Therefore the fitting of the door opener can be very time-consuming and therefore cost-intensive. In the case of fitting and dismantling several times it is also possible for the locking plate and screw heads for fixing the latter to become scratched or otherwise damaged. There is also a risk of the loosening or breaking off of the connecting cables for an electrical operation of the door opener.